ABSTRACT
Bulk compression of polymers causes a decrease of the free volume and is accompanied by a reduction of the intensity of macromolecules segmental motion and the motion of introduced particles. Consequently, the activation volume is always positive which agrees with the prediction of the activation theory and free volume model. The experimental value of activation volume calculated from an angle of the slope of baric dependences decreases with pressure. So, the experimental values of the activation volume depend on pressure. This chapter explains the dependence of activation volumes on particle size and structure for various types of molecular motion. Activation volumes of translational diffusion and large-amplitude rotation of particles are of the same order of magnitude and do not differ sharply from a molecule volume. More regorous calculation of the activation parameters can be performed on the basis of the equation deduced with the help of the thermodynamics.
